Parts for your 2016 Subaru Legacy-Knock sensor

2016 Subaru Legacy knock-sensor — what it does, where it lives, and when to replace it

Yes, the 2016 Subaru Legacy does use a knock sensor. Subaru’s factory service information for the 2015–2019 Legacy/Outback platform (FB25 2.5‑litre and EZ36 3.6‑litre) specifies knock-sensor monitoring and diagnostics, and Subaru’s parts catalogues list knock-sensor assemblies for these engines. The powertrain control module also sets standard OBD‑II knock-sensor fault codes (P0325–P0334), which are only possible if a knock sensor is fitted. On the FB25 there’s a single sensor on the engine block, the EZ36 H6 uses two sensors, one per bank.

The knock sensor is a piezoelectric microphone bolted to the block. It listens for the high-frequency “ping” of detonation and lets the ECU trim ignition timing in real time to protect the engine. That’s how the Legacy squeezes the best from everyday 91–95 RON petrol while keeping knock safely at bay and maintaining smooth, efficient running.

As a service item, the knock sensor itself isn’t on a scheduled replacement list, but it should be treated as critical. Age, heat, over-tightening, or wiring damage can skew readings and push the ECU into knock‑protection mode, which dulls performance and bumps up fuel use. If the MIL is on with a P0325-series code, or there’s persistent pinging, rough running, or lazy throttle response, the sensor and harness deserve a proper look.

• Location: FB25 — typically under the intake manifold on the block, EZ36 — one sensor on each bank.
• Common symptoms: MIL with P0325–P0334, noticeably flat acceleration, higher fuel consumption, occasional ping under load, or timing heavily retarded in live data.
• Replacement tips: Use a quality, correct-spec sensor. Mount to clean, bare metal, don’t use grease or sealant under the pad. Align the sensor as per the workshop manual, torque it precisely (Subaru specs vary by engine, commonly around 24 N·m on late-model flat engines — always check the exact spec). Never overtighten or twist the body by the lead. Inspect and repair the loom and connector if heat-hardened or oil-soaked. Clear codes and verify knock correction and learned values after a road test.
• Access: Often easiest when the intake manifold is off for other work (plugs, PCV, or intake gaskets), which keeps labour tidy and costs down.

Looked after properly, the Legacy’s knock-control system stays transparent to the driver, keeping the engine safe and the fuel bill sensible over many kilometres.

Popular questions about the 2016 Subaru Legacy knock-sensor

Does a 2016 Subaru Legacy have a knock sensor, and how many?
Yes. The 2.5‑litre FB25 has one knock sensor on the block. The 3.6R EZ36 has two, one per cylinder bank. Both are monitored by the ECU and can log P0325‑series codes if there’s a fault.

What are the usual fault codes and symptoms when it fails?
Typical codes include P0325 (circuit malfunction) and related P0326–P0334 range/performance codes. Symptoms can be a check-engine light, dull performance from heavily retarded timing, higher fuel use, or audible pinging under load if control is compromised.

Is it OK to keep driving with a faulty knock sensor?
The ECU will usually play it safe by pulling timing, so the car may still drive but feel sluggish and use more petrol. Continued driving isn’t ideal, if genuine knock occurs, engine stress rises. Prompt diagnosis and repair is the smart move.